[client] Add IPv6 support to usersace bind (#5147)

client/iface/bind/dual_stack_conn.go

@@ -0,0 +1,169 @@
+package bind
+
+import (
+	"errors"
+	"net"
+	"sync"
+	"time"
+
+	"github.com/hashicorp/go-multierror"
+	log "github.com/sirupsen/logrus"
+
+	nberrors "github.com/netbirdio/netbird/client/errors"
+)
+
+var (
+	errNoIPv4Conn  = errors.New("no IPv4 connection available")
+	errNoIPv6Conn  = errors.New("no IPv6 connection available")
+	errInvalidAddr = errors.New("invalid address type")
+)
+
+// DualStackPacketConn wraps IPv4 and IPv6 UDP connections and routes writes
+// to the appropriate connection based on the destination address.
+// ReadFrom is not used in the hot path - ICEBind receives packets via
+// BatchReader.ReadBatch() directly. This is only used by udpMux for sending.
+type DualStackPacketConn struct {
+	ipv4Conn net.PacketConn
+	ipv6Conn net.PacketConn
+
+	readFromWarn sync.Once
+}
+
+// NewDualStackPacketConn creates a new dual-stack packet connection.
+func NewDualStackPacketConn(ipv4Conn, ipv6Conn net.PacketConn) *DualStackPacketConn {
+	return &DualStackPacketConn{
+		ipv4Conn: ipv4Conn,
+		ipv6Conn: ipv6Conn,
+	}
+}
+
+// ReadFrom reads from the available connection (preferring IPv4).
+// NOTE: This method is NOT used in the data path. ICEBind receives packets via
+// BatchReader.ReadBatch() directly for both IPv4 and IPv6, which is much more efficient.
+// This implementation exists only to satisfy the net.PacketConn interface for the udpMux,
+// but the udpMux only uses WriteTo() for sending STUN responses - it never calls ReadFrom()
+// because STUN packets are filtered and forwarded via HandleSTUNMessage() from the receive path.
+func (d *DualStackPacketConn) ReadFrom(b []byte) (n int, addr net.Addr, err error) {
+	d.readFromWarn.Do(func() {
+		log.Warn("DualStackPacketConn.ReadFrom called - this is unexpected and may indicate an inefficient code path")
+	})
+
+	if d.ipv4Conn != nil {
+		return d.ipv4Conn.ReadFrom(b)
+	}
+	if d.ipv6Conn != nil {
+		return d.ipv6Conn.ReadFrom(b)
+	}
+	return 0, nil, net.ErrClosed
+}
+
+// WriteTo writes to the appropriate connection based on the address type.
+func (d *DualStackPacketConn) WriteTo(b []byte, addr net.Addr) (n int, err error) {
+	udpAddr, ok := addr.(*net.UDPAddr)
+	if !ok {
+		return 0, &net.OpError{
+			Op:   "write",
+			Net:  "udp",
+			Addr: addr,
+			Err:  errInvalidAddr,
+		}
+	}
+
+	if udpAddr.IP.To4() == nil {
+		if d.ipv6Conn != nil {
+			return d.ipv6Conn.WriteTo(b, addr)
+		}
+		return 0, &net.OpError{
+			Op:   "write",
+			Net:  "udp6",
+			Addr: addr,
+			Err:  errNoIPv6Conn,
+		}
+	}
+
+	if d.ipv4Conn != nil {
+		return d.ipv4Conn.WriteTo(b, addr)
+	}
+	return 0, &net.OpError{
+		Op:   "write",
+		Net:  "udp4",
+		Addr: addr,
+		Err:  errNoIPv4Conn,
+	}
+}
+
+// Close closes both connections.
+func (d *DualStackPacketConn) Close() error {
+	var result *multierror.Error
+	if d.ipv4Conn != nil {
+		if err := d.ipv4Conn.Close(); err != nil {
+			result = multierror.Append(result, err)
+		}
+	}
+	if d.ipv6Conn != nil {
+		if err := d.ipv6Conn.Close(); err != nil {
+			result = multierror.Append(result, err)
+		}
+	}
+	return nberrors.FormatErrorOrNil(result)
+}
+
+// LocalAddr returns the local address of the IPv4 connection if available,
+// otherwise the IPv6 connection.
+func (d *DualStackPacketConn) LocalAddr() net.Addr {
+	if d.ipv4Conn != nil {
+		return d.ipv4Conn.LocalAddr()
+	}
+	if d.ipv6Conn != nil {
+		return d.ipv6Conn.LocalAddr()
+	}
+	return nil
+}
+
+// SetDeadline sets the deadline for both connections.
+func (d *DualStackPacketConn) SetDeadline(t time.Time) error {
+	var result *multierror.Error
+	if d.ipv4Conn != nil {
+		if err := d.ipv4Conn.SetDeadline(t); err != nil {
+			result = multierror.Append(result, err)
+		}
+	}
+	if d.ipv6Conn != nil {
+		if err := d.ipv6Conn.SetDeadline(t); err != nil {
+			result = multierror.Append(result, err)
+		}
+	}
+	return nberrors.FormatErrorOrNil(result)
+}
+
+// SetReadDeadline sets the read deadline for both connections.
+func (d *DualStackPacketConn) SetReadDeadline(t time.Time) error {
+	var result *multierror.Error
+	if d.ipv4Conn != nil {
+		if err := d.ipv4Conn.SetReadDeadline(t); err != nil {
+			result = multierror.Append(result, err)
+		}
+	}
+	if d.ipv6Conn != nil {
+		if err := d.ipv6Conn.SetReadDeadline(t); err != nil {
+			result = multierror.Append(result, err)
+		}
+	}
+	return nberrors.FormatErrorOrNil(result)
+}
+
+// SetWriteDeadline sets the write deadline for both connections.
+func (d *DualStackPacketConn) SetWriteDeadline(t time.Time) error {
+	var result *multierror.Error
+	if d.ipv4Conn != nil {
+		if err := d.ipv4Conn.SetWriteDeadline(t); err != nil {
+			result = multierror.Append(result, err)
+		}
+	}
+	if d.ipv6Conn != nil {
+		if err := d.ipv6Conn.SetWriteDeadline(t); err != nil {
+			result = multierror.Append(result, err)
+		}
+	}
+	return nberrors.FormatErrorOrNil(result)
+}